Method of spinning collagen solutions



Patented July 5, 1949 UNITED .S TATES METHOD OF SPINNING COLLAGENSOLUTIONS Arthur Cresswell, Stamford, Conn.,- assignor 'to AmericanCyan-amid Company, New YorhJNF-Y a corporation of Maine N Drawing.ApplicatiQn January 14 1949, Serial No. 11,047

2 Claims.

The present invention relates to the spinning .of protein solutions andmore particularly to an improved method of spinning collagen solutions.

In the spinning of filaments from protein mate- :rial such as soy beanprotein, gelatin, casein, col- ..lagen, albumen, keratin and the like,it is customary to make a solution or a suspension of the substance ofthe desired concentration, and jet :the same under pressure through amulti-orifice fate and sodium sulfate.

.In :the spinning of such protein material, ex-

. treme difficulty has been experienced in starting the spinnerette .dueto the fact that in the starting up operation a quantity of the liquidto be spun leaks through the spinnerette and when it .makes contact withthe spin bath, covers the outer surfaces of the spinnerette andassociated parts in a more or less tightly adherent film. Even thoughthis film may be-scraped or cleaned away,

" zdifiiculty is experienced in that the coagulated or regeneratedmaterial tends to form again and clogs the holes of the spinnerette withthe re- ;-sult that either the extrusion pressure is inade- -.q uate toopen them or if they become unplugged,

result in a broken filament.

An improved method of spinning collagen solutions has now beendiscovered which includes the following steps: preparing the collagensolu- 1)i0I1 by dissolving collagen in an aqueous solution of an organicacid, removing fibers and other 1insolubles and extruding said solutionthrough the orifices of a spinnerette, the spinnerette being coated witha basic nitrogen compound contain- 1 ing a long chain alkyl radicalhaving more than .11 carbon atoms, into a spin bath containing analkaline aqueous solution of a sulfate chosen from the group consistingof ammonium, sodium,

zinc, magnesium and mixtures thereof, said coating being insoluble inand repellent of the spin g bath solution.

Animal hides .or skins are, by and large, the most readily availablesource of collagen. It is desirable in using this source of material,that unlimed hides be chosen. These may be fresh or green-salted calfskin, kip skin or other hides which are comparatively. low in elastincontent.

'-- Kip skin-is preferred because the collagen'therefrom is of anoptimum vi-scosity as compared to that of I calf skin. These arelies-bed and unhaired down to the clean cerium, which is that lamina--tion of the animalhlde containing the-=greatst proportionof collagen.If green-salted hides are used, the hides should be soaked before thistreatment and also allowed *to remainin the soaking liquid aftercleaning until substantially-salt free. After cuttingthe cerium-intostrips or small pieces for convenience in handling, the coriu-m iscovered with a dilute solution of an organic acid in the pH rangeof from2 to 4. b Any organic wacid'is satisfactory, although-from 0.05 to0.10iN

formic acid-or 0.5 to 1.0 N acetic acid are preierred. Any otherconcentration of other organic :acids may be used-so long. as the pH ofthe solu- -.tion falls withinthe specified range.

The corium is thus allowed to swell for from 16 to 24 hours in the acidsolution at temperatures between 10 and C. In this swelling-the hideimbibes :from one'tothree times its own weight of liquid but .bymaintainingthe temperature 'atthis point below 30 C., .gelatine-formingconditions are definitely avoided.

Following the swelling, the excess liquid :.is

drained off and the swollen corium mechanically xdisintegrated,.for:example,-by a meat grinder,

shredder or other form of sub-dividing mechanism whichwill break downthe collagen fibers :to the point where dissolution will be facilitated.

Inthe mechanical disintegration step, heat may be developed due tofriction and it is, therefore, -important that the necessary steps-betakento maintain the material during this operation at temperaturesbelow 30 C.

At this stage and if the mechanical disintegration has been fine enough,practically all of the collagen will have gone into solution. Where thiscollagen solution :is highly concentrated, it will gel at 35 C.or below.Therefore, to separate the dissolved collagen from the insolubles, it isneces- -sary to warm itslightly until fluidity has been reached. Thiswill certainly be at a temperature no higher than 60 C. While warming tothis temperature, ifmechanical agitation is carried on, any last tracesof undissolved collagen will dissolve and the -whole may then becentrifuged 'to remove elastin; hair fragments and other in- Solublematter and then filtered as through cotton ..battingpads. The filtratewill be a clear heavily concentrated solution of collagen.

. 'While the preferred source of collagen is'the -acoriumas thisinvolves handling a materialf'of :maxi-mum; collagen .;content-. with11in- 3 solubles, yet as a matter of fact, due to the distribution ofcollagen throughout the animal hide, it may be desirable to disintegratethe entire hide followed by collagen solution in dilute acid and theseparation of the insolubles. Such a process while difierent in the laststep due to the excessive amount of insolubles, does extractsubstantially all the collagen available.

The concentration of the collagen in its solution may be adjusted to adesired content appropriate for spinning, by the addition of a furtheramount of the dilute organic acid solution, such as that used forswelling and solution. It is preferred that the spinning solutioncontain from 5 to collagen, although solutions of lower or highercollagen concentration may be used.

Strong salt solutions have been found satisfactory as coagulating baths,such as a 35% to saturated solution of ammonium sulfate with sufficientfree ammonia to maintain a pH of 7.8 which is an isoelectric point ofcollagen. The free ammonia is useful for the purpose of neutralizing theorganic acid introduced by the spinning solution. Another satisfactorybath is one containing by weight of magnesium sulfate,

buffered with triethanolamine to a pH of 7 .8. Regardless of theparticular coagulant used, it is highly desirable that the bath bemaintained at from 20 to C.

A considerable amount of experimentation has been carried on to providea coating on spinnerettes which are usually composed of stainless steel,Monel metal, gold, platinum, palladium, rhodium, tantalum or alloyscontaining some or all of them, which will prevent the initial adhesionof the collagen material to the surface of the spinnerette. Substancesfound suitable in the spinning of viscose rayon filaments, such aslauryl pyridinium chloride and cetyl pyridinium chloride dissolved inthe spinning bath were completely without effect in preventing initialadhesion of collagen material. Inasmuch as it appeared that greasy orwaxy solids might have promise, a number of hydrocarbons such asparaffin, mineral oil and the like, were tried without success. Again,fatty acids such as stearic acid, palmitic acid and the like completelyfailed to overcome the difficulty. The higher alcohols, such as laurylalcohol, the higher esters such as stearyl glyceride or palmytylstearate completely failed to accomplish the desired purpose.

It was not until spin bath insoluble and repellent basic nitrogencompounds containing a long chain alkyl radical having twelve carbonatoms or more were tried that any sort of reasonable success occurred.These compounds, on the other hand, are outstanding in avoidingdifficulties heretofore experienced in starting up operations withcollagen material.

Where these compounds are heavy liquids, they may be applied as such orsmeared over the outer surface of the spinnerettes and into the orificestherein. Where the substances are very viscous liquids, plastics orsolids, they may be thinned or dissolved with organic solvents known asfat solvents such as volatile hydrocarbons such as benzene, gasoline andxylol and the chlorinated hydrocarbons such as chloroform, carbontetrachloride or the like which may be readily volatilized.

Perhaps the most suitable class of materials for this purpose are thephosphatides of which lecithin is preferred. However, sphingomyelins andcephalines may also be used. Other materials eminently satisfactory arestearamide, stearylamine, stearylguanidine, laurylamine, N,N-dimethyldodecylamine, B-stearoxypropylamine, myristylamine,G-octadecoxypropylamine, N,N- distearylalanyl amide, as well as the longchain alkyl cyanamides, dicyandiamides, melamines, guanamines,biguanides, guanylureas and the like where in all cases the alkylradical has 12 or more carbon atoms.

Where the material is applied to the spinnerette in the form of adilution or solution, chloroform and benzene are entirely satisfactory.It is preferred to make solutions containing from .01% to even as highas 25% in practice. It only becomes necessary to dip the spinnerette ina dilution or solution of the compound or to apply the same to thespinnerette either as a spray or with a brush and then cause the solventto evaporate with the required amount of heat. Obviously the heatapplied to cause evaporation of the solvent should be well below themelting point of the material used so as not to cause an abnormal fiowwhich might clog the apertures. It has been found desirable during thesolvent evaporation step to maintain a flow of gas such as air,nitrogen, carbon dioxide or the like through the spinnerette so as tokeep the apertures from clogging with the coating material, whilepermitting the formation of a film thereon.

Such a treatment upon evaporation of the solvent deposits a very thinfilm on the spinnerette closely adherent to the surface thereof.

Such a coated spinnerette not only avoids the dimculty of the stickingthereto of collagen solutions or suspensions in the starting upoperations but maintains the spinnerette in a perfectly free flowingstate. It has been found, for instance, that a dilute organic acidsolution of collagen containing from 5-15% of the latter may besatisfactorily extruded through a metal spinnerette as above when coatedwith a film of lecithin deposited from a chloroform solution thereof,immersed in an aqueous spin bath including ammonium sulfate from 35% tosaturation and sufficient ammonia to maintain the pH of the bath atabout 7.8, without initial sticking and for long periods of time withoutthe production of imperfect filaments.

This application is a continuation in part of my copending applicationSerial No. 580,081, filed February 2'7, 1945.

While the invention has been described with particular reference tospecific embodiments, it is to be understood that it is not to belimited thereto but is to be construed broadly and restricted solely bythe scope of the appended claims.

I claim:

1. In a method of spinning collagen solutions prepared by dissolvingcollagen in an aqueous solution of an organic acid, removing fibers andother insolubles, the improvement which includes extruding the solutionthrough the orifices of a spinnerette, the spinnerette being coated witha basic nitrogen compound containing a long chain alkyl radical havingmore than 11 carbon atoms, into a spin bath containing an alkalineaqueous solution of a sulfate chosen from the group consisting ofammonium, sodium, zinc. magnesium and mixtures thereof, said coatingbeing insoluble in and repellent of the spin bath solution.

2. The method of claim 1 in which the spinnerette is coated withlecithin.

ARTHUR CRESSWELL.

No references cited.

